Author: Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors "The Garden Professors" Facebook group - www.facebook.com/groups/GardenProfessors Books: http://www.sustainablelandscapesandgardens.com

Podcasts are here!

Today marks a grand experiment…I’ve made the leap into podcasting. Each episode is less than 30 minutes and contains (among other things) an outdoor interview with someone who does something interesting with gardens and landscapes. This week’s podcast features Seattle landscape designer Richard Greenberg, who took me on a tour of a garden he’s been working on for 20 years:


Linda with Richard Greenberg

The nice thing about having the blog host the podcasts is that I can include some photos from my interview sites.  Here are some shots of this lovely (but tiny) urban landscape, which features a huge sequoia right in the middle.


Yes, a sequoia in the middle of the garden


Fritillaria, I assume? (Please don’t mock my taxonomic ignorance)


Very cool iris

Please let me know what you think of the podcast; you can email me directly or post a comment on the blog.  Suggestions for future podcasts are most welcome!

Cool achlorophyllous plant

Can’t get anything past our blog readers!  Yes, from the highly cropped photo on Friday two readers quickly recognized emerging Indian pipe (Monotropa uniflora):

These plants have no chlorophyll, instead relying on fungal partners who colonize both their roots and the roots of nearby photosynthetic plants.  So ultimately this is a parasitic species, as it takes resources from the photosynthesizers in its root network without reciprocal benefit.

These are not commonly found plants, so I think it’s really cool that they appeared in such profusion in a home landscape.

A Garden Professor is most severely vexed

I’ve been thinking a lot about Jeff’s recent post on “What happens to the horticulturist.” It’s true – universities rely more and more on faculty-generated grants for funding, so new hires tend to be in “hot” areas of research.  Fewer horticultural generalists are hired in teaching/research positions, and the same is true for Extension – the educational outreach arm of land-grant universities.

Many of you might not even know what Extension really is.  In my opinion, that’s because Extension as a whole has done a pretty poor job of evolving with the times.  When small farms were the mainstay of life for many people, farmers relied on practical, science-based information provided by university Extension services.  We’ve become an increasingly urbanized society, but Extension just hasn’t kept up.  The bulk of the research and information coming from plant and soil science departments is still geared towards production agriculture.  It’s of little immediate use for the majority of us living in urban areas.

So we have an imbalance:  there are increasing numbers of people living in urban areas who want good information on home gardens and landscaping, and decreasing university resources to fill those gaps.  Nature hates a vacuum, and this information gap is quickly filled with all kinds of stuff: some good, some bad, some dangerous, some illegal.  The very worst offenders, in my opinion, are the fear mongererss with most definite agendas but no solid evidence to support their claims.  For instance: I’m always skeptical when I hear about an article in an “obscure journal” being the only source of new information. If there was something new out there on an important topic, the researchers would not be publishing in an “obscure” journal. It would be in a highly visible and highly regarded scientific journal.  In any case, the information would be easy to find and discuss, not hidden away in a secret location.

I don’t have a good way to end this post, because I don’t have an easy answer to the problems that both Jeff and I see in horticulture departments and in Extension.  Do you?

Voodoo and the evil eye

Friday’s “evil frog eye” was actually part of a voodoo lily (Dracunculus vulgaris), found growing in a drainage ditch in California (I’ve seen one in a drainage ditch in Seattle as well):

Obviously this introduced garden ornamental has escaped cultivation and is now “going rogue.”  Will it become a nuisance weed? Will it displace native species? Should it be banned from sale by nurseries?

Sigh.

In defense of weeds?

Blog reader Shawn sent this link to me yesterday. It’s a pretty short take on a complex topic, but even so I was troubled by the perception that all nuisance weed species are our own fault.

Sure, it’s true that humans have moved plants or plant parts around with them for centuries. Sometimes it’s been deliberate, and sometimes it’s been accidental. But other animals also move plants around, especially seeds. When we draw this kind of distinction between what we do and what other animals do, philosophically we are removing ourselves from the natural world. True, we have technology and all kinds of other human inventions, but as a species we are still part of the biosphere.


Ivy’s little dispersal units – spread by birds

Philosophical issues aside, there’s another part of this blithe acceptance of weedy species that concerns me. Though plants take advantage of animals as a means of dispersal, the rate at which nonnative, weedy species are spreading and colonizing new environments is unprecedented (this is where technology comes in). Ecosystems can adapt to new species and other environmental challenges – but when the rate is accelerated, the adaptive process is impaired. Thus, some native species go extinct when the rate of change is too great.


Ivy left to its own devices in a natural area

These are basic ecological concepts – and we ignore them at our own peril.

Hot weather and not-so-hot advice

Today I was sent a link to a posting on “droopy leaves.”  Essentially, it suggests that droopy leaves are a means to conserve water on hot days and that watering these plants causes more problems than it solves because the roots don’t get enough oxygen.  A link to the science of transpiration is provided.  The advice is to wait until the evening and if the plants perk back up, then they didn’t need water after all.

This is one of those maddening articles that has enough science in it to make it sound reasonable, but is ultimately incorrect in its assumptions and advice.  It’s worth looking at the topic in a little more detail.

Some plants are adept at conserving water in hot weather.  Their leaves tend to be small, thick, with a heavy layer of waxes protecting the surface.  Leaves can also move to limit their sun exposure and thus reduce the heat load.  But wilting is not a method of conserving water.  Instead, it’s a sign that water loss (evapotranspiration through the leaves) exceeds water uptake from the roots.  And if you ignore wilt, you do so at your own peril.  Once terminal wilt is reached, it’s all over for that part of the plant.


Wilt.  Sorry it’s a fuzzy photo.

Large, thin leaves, common in many of ornamental, annual and vegetable species, do not conserve water.  Tomatoes, zucchini and black-eyed susans, the plants specifically mentioned in this article, are not water conservers.  Chronic wilting of these and other can eventually cause leaf tip and margin necrosis (or tissue death).  It also reduces growth, so that your yield of tomatoes, zucchini and black-eyed susans will be decreased.

Leaf tip and marginal necrosis from chronic drought stress

So yes, do water your plants if they are wilting in the midday heat!  Use mulches to conserve water!  (You’ll notice in the photograph on the linked site that the plants are in bare soil.)  Fine root systems are generally near the soil surface, and keeping these hydrated keeps them alive.  You won’t see an instantaneous response to watering if plants are already wilting, but they will recover – much better than if you don’t water them at all.

Chlorosis mystery uncovered – maybe

Sorry about the long wait in discussing the weekend’s post!  (Technical troubles with access here in BlogVille.)  In any case, many of you zeroed in on the defunct lime kiln as a possible pH adjuster.  It would have been really interesting during those years to see how materials were processed – for instance, was there a lot of lime dust that settled over the area?  Where did the limestone come from – was it carted in by train or was it local?  Were chlorosis problems visible then?

In any case, my educated guess is that a lot of limestone chunks brought to the area for processing were left scattered around the site and were eventually buried over time.  Plants recolonized the area, but where these chunks of limestone are sited we have pockets of chlorosis.  The only way to tell for sure would be to test the soil pH, and I did not have pH strips in my backpack.

An artifact from the old settlement, long since covered by the forest.

Interveinal chlorosis mystery

Today my family took our annual 4th of July weekend hike.  We ended up on a fairly new trail through the Robe Canyon Historic Park.  It was a gorgeous day and we saw all manner of plants and animals.  The highlight of this trail is an old lime kiln; bricks and other remnants of early settlers are scattered around the area.  The kiln closed in the 1930’s.  (The hot link embedded in the park name leads to a 2004 article about the trail and the history of the site.)

Ever on the lookout for interesting plants or plant problems, I found many of our native species with definite signs of interveinal chlorosis.  This is indicative of a foliar deficiency of iron or manganese. These forest soils are rarely deficient in either nutrient, and they also tend to be acidic (meaning that it’s easy to take up iron and managanese; alkaline soils inhibit uptake).

So why are these native plants, naturally growing on native soils, showing iron and/or manganese deficiency?Answer on Monday!